Infectious Diseases — MCQs

Rickettsial organisms infect humans worldwide, although geographic locations may be limited for some species and possibly produce some challenges in medical diagnosis. All are obligate intracellular parasites, except C. burnetii, and transmitted by an insect vector. Typhus, spotted fever, and scrub typhus share which of the following manifestations of disease?

Q968

A 25 yr. old girl admitted as a case of septic abortion with tricuspid valve endocarditis. Vegetation from the valve likely to affect will be

Q969

'Malignant pustule' is -

Q970

A person with AIDS related complex is most likely suffering from:

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 961: Which of the following statements is true about mumps?

A. Mumps orchitis frequently leads to infertility
B. The patient is not infectious prior to clinical parotid enlargement
C. Salivary glands involvement is limited to parotid
D. Meningoencephalitis can precede parotitis (Correct Answer)

Explanation: ***Meningoencephalitis can precede parotitis*** - While **parotitis** is the most common manifestation of mumps, **meningoencephalitis** can occur as a complication and, in some cases, may appear before the onset of salivary gland swelling. - The mumps virus can directly infect the central nervous system, leading to neurological symptoms independent of or concurrent with glandular involvement [1]. *Mumps orchitis frequently leads to infertility* - While mumps **orchitis** (inflammation of the testes) can occur, especially in adolescent and adult males, it **rarely** leads to complete infertility, and more commonly affects only **one testis** if it impacts fertility at all. - The risk of bilateral testicular atrophy and subsequent infertility is low, occurring in a small percentage of affected individuals. *The patient is not infectious prior to clinical parotid enlargement* - Individuals infected with mumps are **infectious** typically **1-2 days before** the onset of parotid swelling and up to 5 days after, making transmission possible before clinical symptoms are apparent. - The virus is shed in respiratory secretions during this **prodromal period** and early stages of parotitis. *Salivary glands involvement is limited to parotid* - While the **parotid glands** are most commonly affected in mumps, the **submandibular** and **sublingual glands** can also be involved, though less frequently. - Mumps is a systemic viral infection that can affect various glandular tissues, not just the parotid.

Question 962: A 45 day - old infant developed icterus and two days later symptoms and signs of acute liver failure appeared. Child was found to be positive for Hbs Ag. The mother was also HBs Ag carrier. The mother's hepatitis B serological profile is likely to be ?

A. Mother infected with mutant HBV
B. HBs Ag positive only
C. HBs Ag and Hbe Ag positivity (Correct Answer)
D. HBsAg and anti-HBe antibody positivity

Explanation: ***HBs Ag and HBe Ag positivity*** - The infant developed **acute liver failure** early in life (45 days old) and tested positive for **HBsAg**, suggesting vertical transmission from the mother. [1] - For vertical transmission to lead to **acute, severe infection** in the neonate, the mother must have a high viral load and be highly infectious, which is indicated by **HBeAg positivity**. *Mother infected with mutant HBV* - While mutant HBV can cause severe disease, there's no direct evidence in the scenario to suggest a **mutant strain** over a highly replicative wild-type virus. - **Precore and basal core promoter mutants** are generally associated with HBeAg-negative chronic hepatitis B, not necessarily acute neonatal infection. *HBs Ag positive only* - Being **HBsAg positive only** (without HBeAg) usually indicates a lower level of viral replication and infectivity. [1] - This scenario would make severe vertical transmission leading to **acute liver failure** in an infant less likely. *HBsAg and anti-HBe antibody positivity* - **Anti-HBe antibody positivity** indicates seroconversion from HBeAg, signifying a phase of lower viral replication and reduced infectivity. [1] - This profile would be less likely to result in the acute, severe neonatal infection observed, as the mother's viral load would typically be lower.

Question 963: The tick-borne hemorrhagic fever found in Karnataka state is:

A. Japanese encephalitis
B. Kyasanur forest disease (Correct Answer)
C. Epidemic nephrosonephritis
D. Lassa fever

Explanation: Kyasanur forest disease - **Kyasanur Forest Disease (KFD)** is a **tick-borne hemorrhagic fever** endemic to **Karnataka, India**, particularly in the Shivamogga district. - The disease is caused by the **Kyasanur Forest Disease virus (KFDV)**, a member of the *Flaviviridae* family, transmitted to humans through the bite of infected ticks, primarily *Haemaphysalis spinigera*. *Japanese encephalitis* - **Japanese encephalitis** is a **mosquito-borne viral disease** that can cause encephalitis, but it is not typically characterized as a hemorrhagic fever and is not specifically linked to ticks in Karnataka. - While it can cause neurological symptoms, the primary vector is **mosquitoes**, not ticks, and its epidemiology differs from KFD. *Epidemic nephrosonephritis* - **Epidemic nephrosonephritis** (also known as **Hemorrhagic Fever with Renal Syndrome - HFRS**) is caused by **Hantaviruses** and is typically transmitted through contact with rodent urine, feces, or saliva. - It primarily affects the kidneys and can cause hemorrhagic manifestations, but it is **not tick-borne** and is not the specific hemorrhagic fever found in Karnataka. *Lassa fever* - **Lassa fever** is an **acute viral hemorrhagic illness** caused by the Lassa virus, which is endemic to West Africa and is primarily transmitted to humans through contact with food or household items contaminated with the urine and feces of **multimammate rats (Mastomys natalensis)**. - It is **not found in India** and is not transmitted by ticks.

Question 964: Kallu, a 22 year old male had an outing with his friends and developed fever of 38.50C, diarrhoea, and vomiting following eating chicken salad, 24 hours back. Two of his friends developed the same symptoms. The diagnosis is -

A. Vibrio cholerae
B. Salmonella enteritis (Correct Answer)
C. Bacillus cereus
D. S. aureus

Explanation: ***Salmonella enteritis*** - The onset of **fever**, **diarrhea**, and **vomiting** 24 hours after eating potentially contaminated chicken salad, affecting multiple individuals, is highly characteristic of **Salmonella food poisoning** [2], [4]. - **Salmonella enteritidis** is a common cause of foodborne illness associated with poultry and eggs, and causes an **invasive infection** leading to systemic symptoms like fever [2]. *Vibrio cholerae* - **Vibrio cholerae** typically causes profuse, watery diarrhea ("rice-water stools") with severe dehydration, a much shorter incubation period (hours), and less pronounced fever, if any [3]. - It is usually associated with contaminated water sources in endemic areas and not typically isolated cases from common food items like chicken salad. *Bacillus cereus* - **Bacillus cereus** can cause two types of food poisoning: diarrheal (onset 6-15 hours) and emetic (onset 1-6 hours), usually associated with **reheated rice** [1]. - While it causes vomiting and diarrhea, the 24-hour incubation period for the symptoms described makes it less likely, and fever is less prominent than with Salmonella [1], [4]. *S. aureus* - **Staphylococcus aureus** food poisoning typically has a very rapid onset (1-6 hours) after consuming food contaminated with preformed toxins [2], [4]. - Symptoms are predominantly **nausea**, **vomiting**, and abdominal cramps, with diarrhea sometimes present, but fever is uncommon or mild due to the toxin-mediated nature rather than an invasive infection [2].

Question 965: True regarding Dengue fever is all, EXCEPT -

A. Transmitted by Anopheles mosquito (Correct Answer)
B. Haemorrhagic tendency
C. Spontaneous remission
D. Fever is saddle back type

Explanation: ***Transmitted by Anopheles mosquito*** - Dengue fever is primarily transmitted by the **Aedes aegypti** mosquito, not the Anopheles mosquito. - The **Anopheles mosquito** is the primary vector for **malaria**, not dengue. *Haemorrhagic tendency* - **Haemorrhagic manifestations**, ranging from mild petechiae to severe gastrointestinal bleeding, are a well-known feature of dengue fever, particularly in severe cases [1]. - This tendency results from **platelet dysfunction** and **increased vascular permeability** [1]. *Spontaneous remission* - Most cases of classic dengue fever resolve spontaneously within a week without specific treatment, indicating a tendency for **spontaneous remission**. - Supportive care, including **hydration** and **rest**, is typically sufficient for recovery. *Fever is saddle back type* - The fever pattern in dengue is often described as **biphasic** or "saddle-back," where the fever subsides for a day or two and then returns. - This unique fever curve is a characteristic clinical feature of dengue infection [1].

Question 966: Which is not associated with community acquired pneumonia

A. Pneumococcus
B. Chlamydia
C. Pseudomonas aeruginosa (Correct Answer)
D. Legionella

Explanation: ***Pseudomonas aeruginosa*** - **_Pseudomonas aeruginosa_** is most commonly associated with **hospital-acquired pneumonia** (HAP) or pneumonia in individuals with **structural lung disease** (e.g., cystic fibrosis, bronchiectasis) [1] or **immunocompromised states**. - Its presence in community-acquired pneumonia (CAP) is **rare** and usually indicates severe, complicated cases or specific risk factors not typical for CAP. *Pneumococcus* - **_Streptococcus pneumoniae_** (Pneumococcus) is the **most common cause** of typical bacterial community-acquired pneumonia (CAP) [1]. - It presents with **acute onset** of fever, chills, productive cough, and lobar infiltrates on chest X-ray [1]. *Chlamydia* - **_Chlamydia pneumoniae_** is a common cause of **atypical community-acquired pneumonia**, often presenting with a more gradual onset and milder symptoms [1]. - It can cause a **"walking pneumonia"** with symptoms like persistent cough, sore throat, and low-grade fever. *Legionella* - **_Legionella pneumophila_** is a cause of severe **atypical community-acquired pneumonia**, often linked to contaminated water sources [1]. - It can present with systemic symptoms such as **gastrointestinal upset**, **neurological symptoms**, and hyponatremia, in addition to respiratory symptoms.

Question 967: Rickettsial organisms infect humans worldwide, although geographic locations may be limited for some species and possibly produce some challenges in medical diagnosis. All are obligate intracellular parasites, except C. burnetii, and transmitted by an insect vector. Typhus, spotted fever, and scrub typhus share which of the following manifestations of disease?

A. Arthritis
B. Common vector
C. Fever and rash (Correct Answer)
D. Short incubation period (<48 hours)

Explanation: ***Fever and rash*** - **Fever** is a universal response to infection, and **rash** is a common dermatological manifestation due to **vascular damage** caused by rickettsial organisms. [1] - The combination of **fever** and **rash** is a hallmark sign in clinical presentations of **typhus**, **spotted fever group rickettsioses**, and **scrub typhus**. [1] *Arthritis* - While arthritis can occur in some infectious diseases, it is **not a characteristic or common manifestation** across all rickettsial diseases mentioned. - The primary targets for rickettsial organisms are **endothelial cells**, leading to vasculitis, rather than direct joint involvement. *Common vector* - The rickettsial diseases mentioned are transmitted by **different vectors**: typhus by **lice or fleas**, spotted fever by **ticks**, and scrub typhus by **chiggers**. [1] - Therefore, they do **not share a common insect vector**. *Short incubation period (<48 hours)* - Rickettsial diseases typically have an incubation period ranging from **5 to 14 days**, which is considerably longer than 48 hours. [1] - A very short incubation period (<48 hours) is more typical of **bacterial food poisonings** or **viral infections** like influenza.

Question 968: A 25 yr. old girl admitted as a case of septic abortion with tricuspid valve endocarditis. Vegetation from the valve likely to affect will be

A. Lung (Correct Answer)
B. Brain
C. Spleen
D. Liver

Explanation: ***Lung*** - Injected drug users often develop **tricuspid valve endocarditis**, which can lead to septic emboli lodging in the **pulmonary vasculature and causing lung damage** [2]. - Right-sided endocarditis, seen here with tricuspid valve involvement, typically embolizes to the **lungs**, causing symptoms such as **pneumonia, lung abscesses, or pulmonary infarcts** [3]. *Brain* - Emboli to the brain usually originate from the **left side of the heart**, such as the mitral or aortic valves, or from peripheral venous clots that paradoxically cross through a septal defect. - While possible in rare cases of paradoxical emboli, this is not the typical or most likely site for embolization from isolated tricuspid valve endocarditis. *Spleen* - **Splenic emboli** are more commonly associated with **left-sided endocarditis**, where vegetations can dislodge and travel systemically [1]. - While the spleen is part of the systemic circulation, it is not the primary target foremboli originating from the right heart. *Liver* - The liver receives blood from both the hepatic artery (systemic circulation) and the portal vein (gut circulation), but it is not a common site for embolization from **right-sided valvular endocarditis**. - Emboli from the right heart would first pass through the lungs before reaching the systemic circulation that supplies the liver.

Question 969: 'Malignant pustule' is -

A. Malignant melanoma
B. Marjolin's ulcer
C. Proliferating rodent ulcer
D. Anthrax ulcer (Correct Answer)

Explanation: **Anthrax ulcer** - The term "malignant pustule" is a classic description for the skin lesion observed in **cutaneous anthrax**. - It refers to the characteristic progression of a papule to a vesicle, then a central **necrotic ulcer (eschar)** surrounded by edema. *Malignant melanoma* - This is a **skin cancer** originating from melanocytes, characterized by irregular borders, varying colors, and evolving size (ABCDEs). - It does not present as a pustule and has a different pathological and clinical course. *Marjolin's ulcer* - This is a **squamous cell carcinoma** that arises in chronic wounds, scars, or areas of chronic inflammation, such as burn scars, venous ulcers, or osteomyelitis. - It is a type of cancer, not an infectious pustular lesion. *Proliferating rodent ulcer* - This term is likely a descriptive phrase referring to a rapidly growing or extensive **basal cell carcinoma (rodent ulcer)**. - Basal cell carcinoma is a slow-growing skin cancer that rarely metastasizes and does not typically present as a pustule.

Question 970: A person with AIDS related complex is most likely suffering from:

A. Opportunistic infection (Correct Answer)
B. Generalized lymphadenopathy
C. Cancer related to AIDS
D. Herpes zoster

Explanation: ***Opportunistic infection*** - AIDS-related complex (ARC) describes symptoms experienced by individuals with **HIV infection** before the full onset of AIDS, often including systemic symptoms and increased susceptibility to infections. - The immunocompromised state in ARC makes patients highly vulnerable to **opportunistic infections**, which are common presentations during this phase [1]. *Generalized lymphadenopathy* - While **generalized lymphadenopathy** is a common feature of HIV infection and can be part of ARC, it is a symptom or sign, not the primary "suffering" that defines much of the morbidity [1]. - **Persistent generalized lymphadenopathy (PGL)** is characterized by enlarged lymph nodes in two or more extrainguinal sites for over three months, often seen in early HIV infection, but it *doesn't fully encompass* "suffering" as broadly as opportunistic infections do [1]. *Cancer related to AIDS* - **AIDS-defining cancers** (e.g., Kaposi's sarcoma, non-Hodgkin lymphoma) are more characteristic of full-blown AIDS, when the immune system is severely compromised (CD4 count typically < 200 cells/µL). - While the risk of certain cancers increases with HIV, and some may occur in ARC, **opportunistic infections** are a more ubiquitous and defining feature of the "suffering" associated with the ARC stage [1]. *Herpes zoster* - **Herpes zoster**, or shingles, results from reactivation of the varicella-zoster virus and is more prevalent and often more severe in HIV-positive individuals, including those with ARC [1]. - However, it represents *one specific type* of opportunistic infection or condition, and the question asks what the person is "most likely suffering from" in a general sense within ARC, for which opportunistic infections are the overarching category.

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Principles of Antimicrobial Therapy

Practice Questions

Fever of Unknown Origin

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HIV/AIDS and Related Infections

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Tuberculosis and Mycobacterial Diseases

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Tropical and Parasitic Infections

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Viral Infections (Hepatitis, Herpes, etc.)

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Healthcare-Associated Infections

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Fungal Infections

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Sepsis and Septic Shock

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Infection in Immunocompromised Hosts

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Emerging and Re-emerging Infections

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Antimicrobial Resistance

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Vaccination Principles

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